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McIntosh C26 hum after recaping
McIntosh C26 hum after recaping
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Old 6th November 2014, 07:25 PM   #1
Tropentarn is offline Tropentarn  United Kingdom
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Default McIntosh C26 hum after recaping

Ladies and Gentlemans,

I ask for your help again. After recapping my C26 preamp, there is a hum if I put the loudness control pot close or on flat. Is quiet in the region from 11 to4 a clock position. Can be the potentiometer?
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Old 6th November 2014, 07:48 PM   #2
rayma is offline rayma  United States
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Originally Posted by Tropentarn View Post
Ladies and Gentlemans,

I ask for your help again. After recapping my C26 preamp, there is a hum if I put the loudness control pot close or on flat. Is quiet in the region from 11 to4 a clock position. Can be the potentiometer?
There's a shielded cable connecting one end of the loudness control, can the shield have been disconnected?

McIntosh C26 Manual - Stereo Pre Amplifier - HiFi Engine
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Old 6th November 2014, 08:14 PM   #3
Tropentarn is offline Tropentarn  United Kingdom
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I have checked the shield for continuity with the ground. It is ok. I have checked all ground solder joints, replaced diodes. No success
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Old 10th November 2014, 08:54 AM   #4
gmphadte is offline gmphadte  India
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One possibility... reverse connected cap.

Gajanan Phadte
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Old 6th May 2021, 03:27 PM   #5
andredonahue is offline andredonahue  Canada
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Default McIntosh C26 loudness humming after recap solved.

McIntosh C26 loudness control humming solved !


Do not place ground leads on the first stage electrolytic or star ground off that first stage ( there other ground paths elsewhere which create a loop and get you into trouble! ). Respect the same grounding scheme as the original can electrolytics as per on the schematic. First stage cap ground is attached to ground lug of center tap of power transformer. And you're all set !
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Old 13th October 2021, 04:41 PM   #6
Marc369 is offline Marc369
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Thumbs up Hum after recap

Thank you very much for your post.
I had hum after recap and by applying C304a directly to the transformer ground it was totally gone
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Old 13th October 2021, 09:54 PM   #7
Elvee is offline Elvee  Belgium
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Yet another recapping adventure that went badly wrong.
This one had a happy end for some, but apparently not for the OP.
How many times will we need to hammer this: if it ain't broke, don't fix it.
Most quality caps used in quality gear do not age, or do so gracefully.
They sometimes fail, and need to be replaced, but generally they are perfectly OK.
I still have unopened bags of Siemens E-lytics dating back from the mid-seventies, and I when I use them (yes, I still use them), I don't even care to reform them: I just put them to work in circuit, and they just work. They are bulky, by today's standards, but they are excellent, even by today's standards: they manage to outperform some modern low-ESR types.
I have had to replace numbers of worn caps, even in equipments made by reputable manufacturers, like HP, MacIntosh and others, but I only do so when it is actually necessary.
So-called "preventative maintenance" often ends up doing more harm than leaving things in their condition.

If you are still unconvinced, search for recapping stories that turned sour on the forum. It should make you think twice about "ornamental tweaks", like unnecessary recappings.
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Old 13th October 2021, 09:59 PM   #8
MikePP is offline MikePP
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yeah



Or at least do it in stages (and retest at each stage , then you will know where you've messed up.
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Old 13th October 2021, 10:16 PM   #9
as_audio is offline as_audio
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Cap replacement - so called "recapping" does a lot of harm to new and vintage gear
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Old 13th October 2021, 10:25 PM   #10
nironiro is offline nironiro  Croatia
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Just as Elvee said: If it ain't broke, don't fix it.
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